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Abstract Detail


Stanfield, Ryan [1], Bartlett, Megan [2].

Turgor Regulation of Sucrose Loading Transporters in the Phloem Decouples Plant Water Status from Translocation.

The xylem and phloem are highly coordinated, and phloem transport may experience catastrophic failure during drought. Although phloem transport remains difficult to study due the sensitive nature of the tissue, modeling approaches are used to address the physiological linkages of drought and phloem transport on carbon partitioning. Previous models have predicted that with passive phloem loading, carbon export efficiency is influenced by the regulation of plant water status through stomatal control. However, we know less about how an active loading process may respond to drought conditions. Here we present a coordinated xylem and phloem transport model using an active loading process to determine the amount of sucrose unloaded to sink tissue. We specifically addressed how changes in phloem architecture, sucrose transporter kinetics, stomatal control traits, and changes in plant water status impacted sucrose export. We found that the shutting off of sucrose transporters at excessive turgor pressures prevented failure of sap transport due to excessive viscosity increases. This importantly decouples total sugar export to sinks from xylem water potentials and phloem resistance in active loading species. Substantiating these results with a meta-analysis, we also found that phloem resistance does not correspond to a plant’s driest water potential between species. We hypothesize that a turgor driven sucrose transporter response plausible as phloem turgor has been shown to regulate sucrose loading rates. This frees phloem architecture from being driven purely by drought impacts on transport. Instead, we suggest that the active loading strategy may allow for a higher resistance phloem to enable greater control of sealing in the event of pathogen infection or wounding.

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1 - University of California, Davis, Viticulture and Enology, One Shields Ave. , RMI North, Davis, CA, 95616, USA
2 - University of California, Davis, One Shields Ave., RMI North, Davis, CA, 95616, United States

Phloem Transport
Sucrose Transporter Kinetics  
Carbon Allocation
Stomatal Regulation
Phloem Architecture.

Presentation Type: Oral Paper
Session: ECOPH2, Ecophysiology II
Location: /
Date: Tuesday, July 20th, 2021
Time: 1:30 PM(EDT)
Number: ECOPH2012
Abstract ID:478
Candidate for Awards:None

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